Biochips are components used for example in chemical analysis (including Proteomic and Molecular analysis) either to host a test reaction and/or to supply samples under test or reagents. Generally, a Biochip comprises a solid substrate on which is arranged one or more test sites at which a reaction can take place in use. For instance, the test site may carry one or more reagents (e.g. ligands such as antibodies or antigens) adsorbed to the substrate, which are activated by the addition of a sample substance (e.g. analytes present in the sample bind to specific ligands). Such chips are sometimes referred to as a “lab on a chip” and can also incorporate tools for controlling steps of a reaction. As an example, one Biochip supplied by Randox Laboratories Ltd is used as a medium for performing multiplex analysis of biological samples using a chemiluminescence method. In this example, the Biochip takes the form of a small ceramic chip with a specialized surface preparation which is sensitive to environmental degradation. Therefore the Biochip is generally delivered in an environmentally sealed format, usually evacuated, sealed foil bags.
For instance, the Evidence™ analyzer by Randox Laboratories Ltd uses biochips which are fitted into a plastic holder defining three recesses arranged in a line. Each recess is approximately square and sized to just accommodate a biochip, which is also square, with a small clearance to allow the chip to be placed. The “strip” of three mounted biochips are placed within a sealed foil bag for storage, which is then opened when the biochips are required for use. The plastic holder may be placed on a carrier alongside two further strips of three biochips to form a 3×3 array of biochips. The carrier has a keying feature for engagement with a robotic arm such that the array can be transported within the analyzer via robotic handling. This configuration is useful for batch analysis but not suitable for randomized work loads.
In some types of analyzing apparatus for performing chemical or biological tests, individual chips must be available to be used in any order required by the lab's workload. Therefore individual chips could remain unused onboard the system for days or weeks and are required to remain viable. Further, it can be necessary to supply the apparatus with more than one of each chip type.
Therefore a means of sealing and automatically opening the individual chips at time of use is required.
In some known analyzing apparatus, such as the Evidence™ analyzer mentioned above, biochips are carried in a tray with individual recesses for each biochip. During analysis, reagents and/or samples are dispensed on to the chip within the recess, e.g. by pipetting. This can give rise to “trending” in the results: for instance, reaction sites closest to the position at which the reagent or sample is dropped onto the chip may be exposed to a higher concentration of the reagent or sample than sites further away, due to intermediate sites having bound active components of the reagent or sample as the fluid spreads across the surface of the chip. The test results could therefore be artificially skewed and typically this may be addressed by consistently dispensing the reagent or sample at precisely the same location on the chip, so that the trending may be predicted and compensated for when analyzing the results. A very high degree of control of the reagent and sample dispensing probes is therefore desired.
In addition, at various steps during the analysis, the recess may need to be evacuated (of air, water or other fluid, e.g. sample or reagents) and this is typically performed using a vacuum probe inserted into the recess holding the chip. The vacuum probe movement must be also controlled to a high degree of accuracy in order to avoid contact with the biochip surface itself, which could contaminate the chip and/or damage the test site(s) on its surface.